Thin layer transfers between semiconductor substrates using state of the art bonding approaches, such as the SMARTCUT® technology or other molecular bonding techniques, require that the semiconductor wafers or substrates to be bonded both have a low surface roughness. For instance, EP 1 338 030 B1 discloses methods for forming a thin layer on a thick support, which can involve a first transfer step using the SMARTCUT® technology of a thin layer. The required surface quality for molecular bonding techniques is obtained by extensive polishing processes in order to prepare the substrates before the bonding steps can be performed.
Therefore, there is a need for improved layer transfer techniques. In particular, there is a need for alternative bonding techniques in the semiconductor industry.
This object is achieved with the inventive method for fabricating a substrate, comprising the steps of providing a donor substrate with at least one free surface, performing an ion implantation at a predetermined depth of the donor substrate to form an in-depth predetermined splitting area inside the donor substrate, and providing a layer of an adhesive, in particular an adhesive paste, over the at least one free surface of the donor substrate.
Surprisingly, this method has been found to yield satisfying results with semiconductor materials, as no polishing is required prior to applying the adhesive layer. Thus, an ion layer can be implanted inside a donor substrate, and the substrate can be attached to or with the adhesive layer. The inventive method can, thus, advantageously, be used for mass-production of cheap semiconductor substrates and/or semiconductor structures. Without being restricted to the following, the substrate can be a semiconductor, for example, a semiconductor wafer, a semiconductor substrate, a recycled semiconductor substrate, or even a semiconductor structure.